Allocation of resources in packet-switched data transfer

ABSTRACT

For transferring packets between a wireless data transfer device and a mobile communication network, temporary block flows are formed, and information is transferred in these block flows in one or more packet data traffic channels either in the first direction from the mobile communication network to the wireless data transfer device or in the second direction from the wireless data transfer device to the mobile communication network. In the method, information about the end of the block flow is set in a packet to be transmitted in a block flow when data transfer has stopped. When the transfer of packets in the first direction has stopped, at least one enquiry message is also sent from the mobile communication network to the wireless data transfer device.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not-Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a method according to the preamble ofclaim 1, a data transfer system according to the preamble of claim 13,and a wireless data transfer device according to the preamble of claim18.

(2) Description of Related art including information disclosed under 37CFR 1.97 and 1.98

The term “wireless data transfer system” is generally used to mean anydata transfer system, which enables a wireless data transfer connectionbetween a wireless data transfer device (MS) and fixed parts of thesystem when the user of the wireless data transfer device is moving inthe operating region of the system. A typical wireless data transfersystem is the Public Land Mobile Network PLMN. Most of the wireless datatransfer systems that exist at the time of filing this applicationbelong to so-called second generation wireless data transfer devicesystems, an example of which is the widely known GSM system (GlobalSystem for Mobile telecommunications). The present invention isespecially suitable for the packet-switched wireless data transferdevice systems being developed now. An example of these wireless datatransfer device systems used in this specification is the GPRS system(General Packet Radio Service), the standardization of which is underway now. It is clear that the invention can also be applied in otherwireless data transfer device systems in which packet-switched datatransfer is applied.

The General Packet Radio Service (GPRS) is a new service being developedfor the GSM wireless data transfer device system. The operationalenvironment of the GPRS system comprises one or more subnetwork serviceareas, which are combined as a GPRS backbone network. The subnetworkcomprises several Support Nodes (SN), examples of which used in thisspecification are the Serving GPRS Support Nodes (SGSN), which areconnected to the mobile network (typically via a connection unit to thebase station) so that they can offer packet switched services to thewireless data transfer devices via the base stations (cells). The mobilenetwork offers packet-switched information transfer between the supportnode and the wireless data transfer device. Different subnetworks, inturn, are connected via the GPRS Gateway Support Nodes (GGSN) to anexternal data network, such as a Public Switched Data Network (PSDN).The GPRS service thus enables packet-switched transfer of informationbetween a wireless data transfer device and an external data network,whereby certain parts of the mobile network form an access network.

In order to use the GPRS services, the wireless data transfer deviceperforms at first a GPRS attach, by which it notifies that it is readyfor the transmission of packet data. The attach forms a logical linkbetween the wireless data transfer device and the support node SGSN, andthus enables the transmission of short messages (SMS, Short MessageServices) via the GPRS network, paging via a support node andnotification of packet data to the wireless data transfer device. Whilethe wireless data transfer device is attaching to the network, thesupport node performs the mobility management (MM) operation and useridentification. In order to transmit and receive information, a PacketData Protocol (PDP) is activated, whereby a packet data address to beused in a packet data connection is specified for the wireless datatransfer device, and thus the address of the wireless data transferdevice is known in the gateway GPRS support node. When the attach isperformed, a data transfer connection is established with the wirelessdata transfer device, the support node and the gateway GPRS supportnode, and a protocol (such as (X.25 or IP), a connection address (e.g.X.121 address), Quality of Service and Network Service Access PointIdentifier (NSAPI) are specified for the connection. The wireless datatransfer device activates a packet data connection with an Activate PDPContext Request, in which the wireless data transfer device gives theTemporary Logical Link Identity (TLLI), the type of the packet dataconnection, the address, the required Quality of Service, the NetworkService Access Point Identifier and possibly also the Access Point Name(APN).

The Quality of Service specifies, for instance, how Packet Data Units(PDU) are handled during the transfer in the GPRS network. The Qualitiesof Service defined for connection addresses, for example, are used tocontrol the order of transmission, buffering (packet queues) and therejection of packets in the support node and the gateway GPRS supportnode especially in situations where there are packets to be sent in twoor more connections simultaneously. Different qualities of servicespecify different delays for the transfer of packets between differentends of the connection, different bit rates, and the number of packetsrejected may be different in connections with different qualities ofservice. Four different Quality of Service classes have been formed inthe GPRS system, and these classes specify the Quality of Serviceoffered by the LLC layer to the connection.

Reliability determines whether acknowledgement is used (ARQ) or not (noARQ) in the Logical Link Control (LLC) and Radio Link Control (RLC)layer in data transfer. In addition, reliability determines whetherprotected mode is used in non-acknowledged data transfer, and whetherthe GPRS backbone network uses the TCP or UDP protocol in the transferof packets that belong to the connection.

The attached FIG. 1 shows the operation of a known LLC protocol layer101 in the wireless data transfer device and in the GPRS support node.Block 102 represents the operations of the known RLC/MAC (Radio LinkControl/Media Access Control) layer that are needed between the LLClayer 101 and the wireless data transfer device (not shown).Correspondingly, block 103 represents the operations of the known BSSGP(Base Station Subsystem GPRS Part) layer that are needed between the LLClayer 101 and the closest serving GPRS support node (not shown). Theinterface between the LLC layer 101 and the RLC/MAC layers is called theRR interface, and the interface between the LLC layer 101 and the BSSGPlayers is called the BSSGP interface.

Above the LLC layer 101, there are the known GPRS mobility managementoperations 104, the SNDCP operations 105 and the short message serviceoperations 106, which belong to layer 3 in the layered structuredescribed here. Each of these blocks has one or more connection pointsto the LLC layer 101 for connecting to its different parts. The logicallink control block 107 has a Logical Link-GPRS Mobility Management(LLGMM) control connection to block 104. The mobility managementinformation is routed via the LLGMM connection between the blocks 104and the first LLE (Logical Link Entity) block of the LLC layer. Thesecond 109, third 110, fourth 111 and fifth 112 LLE block are connectedto block 105 via corresponding connections. These blocks are also calledQoS 1, QoS 2, QoS 3 and QoS 4 according to the Quality of Service of thepackets handled by these blocks. The sixth LLE block 113 of the LLClayer is connected to the block 106 via the LLSMS (Logical Link-ShortMessage Service) connection. The Service Access Point Identifiers of thefirst 108, second 109, third 110, fourth 111, fifth 112 and sixth LLEblock are 1, 3, 5, 9, 11 and 7, respectively. Each of these LLE blocksis linked in the LLC layer to the multiplexing block 114, whichprocesses connections via the RR interface to block 102 and further tothe wireless data transfer device, as well as connections via the BSSGPconnection to block 103 and further towards the support node SGSN.

The connection between the multiplexing block 114 and block 102 of thelower level towards the wireless data transfer device is called thetransmission pipe. All packet data flows between the upper parts of theLLC layer and the lower layers 102 go through the same multiplexingblock 114 and transmission pipe. For the packet data transfer of the LLClayer 101 in the GPRS system, it is possible to create Temporary BlockFlows (TBF) between the wireless data transfer device and the mobilenetwork. Such a temporary block flow can be started either by thewireless data transfer device or the mobile network. These temporaryblock flows are temporary block flows of the RLC/MAC layer, in whichinformation of the LLC layer is transferred. A temporary block flow maybe intended for data transfer either from the mobile network to thewireless data transfer device, which is denoted shortly by DL TBF(Downlink TBF) in the signalling diagrams of FIGS. 2, 3 a and 3 b, orfrom the wireless data transfer device to the mobile network, in whichcase it is denoted by UL TBF (Uplink TBF).

FIG. 2 is a signalling diagram of prior art packet data transfer, inwhich temporary block flows are used. The block flow is preferablyformed by means of a control channel, such as PCCCH or CCCH, byconfiguring a packet channel PDTCH. This is represented by block 201 inFIG. 2. When the temporary block flow has been formed, the transfer ofpackets is started (arrow 202). Each RLC packet sent by the mobilenetwork to the wireless data transfer device contains a Final BlockIndicator (FBI). The purpose of this final block indicator is to informthe wireless data transfer device when the mobile network no longer hasinformation to be sent to the wireless data transfer device in the blockflow, whereupon this temporary block flow can be stopped. In order toreceive packets, the wireless data transfer device switches to thePacket Transfer Mode and starts listening to the packet data channel andreceiving packets.

The mobile network sets information about this in the last packet to betransmitted (arrow 203), for example by setting the final bit of thepackets in the packet header field to the value true (e.g. the logicalmode 1). Then the wireless data transfer device knows that it was thelast packet received in this block flow. This packet also contains theRelative Reserved Block Period (RRBP) field, in which the mobile networkcan inform the wireless data transfer device in which time slot thewireless data transfer device can send the acknowledge message. Havingreceived this last packet, the wireless data transfer device transmitsan acknowledgement message (204) to the mobile network in the given timeslot and starts a timer (block 205), such as T3192 in the GPRS system,for time-out consideration. If the RLC Acknowledged Mode has been usedin the block flow, the wireless data transfer device sends asacknowledgement the Packet Downlink Ack/Nack message, in which the FinalAck Indicator (FAI) is set to the value true, preferably the logicalmode 1. The value of this final bit notifies the mobile network thatretransmission of packets is not needed (any more), because all packetshave been received. If the RLC Unacknowledged Mode has been used in theblock flow, the wireless data transfer device sends the Packet ControlAck message as the acknowledgement message. The wireless data transferdevice still continues listening to the packet data transfer channelPDTCH in case the wireless data transfer device would have to send theacknowledgement message again, until the time set in the timer T3192 hasexpired. After this, the wireless data transfer device switches to theidle state. A timer is also started in the mobile network, such as T3193in the GPRS system, when the mobile network has received theacknowledgement message from the wireless data transfer device. Afterthe time specified in the timer has expired, the mobile network releasesthe temporary block flow.

If the wireless data transfer device has packets to be sent in the idlemode, the wireless data transfer device cannot start sending thesepackets directly, but it must at first switch from the idle mode to theactive mode (packet transmission mode). After this, the wireless datatransfer device starts the procedure for forming a temporary block flowin the control channel, such as the above mentioned PCCCH or CCCHcontrol channel (block 206). The transfer of packets from the wirelessdata transfer device to the mobile network can be started after thetemporary block flow has been formed. The signalling performed duringthe formation is represented by arrows 207 and 208, and theconfiguration of the packet channel by block 209. The time needed forthe request for resources and the formation of the temporary block flowmay be as much as several seconds. In practice, an arrangement like theone described above delays the transfer of packets, because the wirelessdata transfer device must first wait for the end of the time-outconsideration and switch to the idle mode before a new temporary blockflow can be formed. In addition, establishing the connection causesextra loading of the control channel. Situations like the one describedabove arise especially in connection with the signalling processes, inwhich the wireless data transfer device must send a reply to a messagesent by the mobile network substantially immediately.

If the mobile network has asked, in connection with the transmission ofpackets, the wireless data transfer device to send acknowledgementmessages, the wireless data transfer device can inform the mobilenetwork of the need to send packets in these acknowledgement messages.However, the mobile network does not always ask for acknowledgements,and so in a situation like this the wireless data transfer device doesnot have a chance to ask for resources for the transfer of packetsbefore the acknowledgement after the reception of the last packet.Because at this stage the temporary block flow has ended and notransmission time slot has been reserved for the wireless data transferdevice, the wireless data transfer device cannot send a request forresources. This means that the wireless data transfer device must switchto the idle mode and back before it can ask for resources for thetransmission of packets.

Even when the acknowledged mode is used, there may be problems insending the block flow request on time. The wireless data transferdevice can set a Channel Request Description IE in the acknowledgementmessage, whereby the mobile network may try to allocate resources forestablishing a temporary block flow from the wireless data transferdevice to the mobile network. In this situation, the mobile networksends a resource allocation message (such as Packet Uplink Assignment)to the wireless data transfer device, after which the wireless datatransfer device can start the transmission of packets. However, in allsituations the wireless data transfer device does not have time to askfor the allocation of resources before it has to send theacknowledgement message. The reason for this may be, for instance, thatpackets of an application layer (e.g. information related to an Internetbrowser, such as information of a home page) are being transmitted in anRLC packet received by the wireless data transfer device in a blockflow, in which case the packet must be moved from the RLC layer to theLLC layer. In the LLC layer, the LLC frame structure is dismantled andtransferred to the TCP/IP layer via the SNDCP layer. From the TCP/IPlayer, the information contained by the packet is transmitted to theapplication. After this, the application can form a reply message, forexample, to be transmitted further via the mobile network. Reversemeasures are then performed, i.e. the information of the applicationlayer is transformed via the intermediate layers to information of theLLC layer and further to RLC packets. The time taken by this wholeprocess may be so long that information about the need to transmitpackets is not received in the RLC layer before the acknowledgementmessage of the RLC layer is sent to the mobile network.

In the GPRS system, the wireless data transfer device has a time of13–26 TDMA frames (one frame is ca. 4.615 ms) to send an acknowledgementmessage. This time is influenced by the value of the RRBP field in thepacket transmitted by the mobile network. This means that the upperlayers of the protocol stack have approx. 60 to 120 ms of time to formthe packet to be transmitted and move it to the RLC layer. In practicalsituations this does not often succeed, and thus the wireless datatransfer device must first switch to the idle mode before a temporarypacket flow from the wireless data transfer device to the mobile networkcan be formed.

BRIEF SUMMARY OF THE INVENTION

The purpose of the present invention is to reduce the above mentioneddrawbacks and to accomplish a more efficient method and system inpacket-switched data transfer between a wireless data transfer deviceand a mobile network. The invention is based on the idea that when thelast packet of each packet transfer has been transferred from the mobilenetwork to a wireless terminal device, such as a wireless data transferdevice, a enquiry message is transmitted from the mobile network to thewireless terminal device, to which enquiry message the terminal devicecan send a reply and when required, ask for resources for data transferfrom the wireless terminal device to the mobile network. If there arepacket data units to be sent in the wireless data transfer device, theformation of a temporary block flow can be started without the wirelessdata transfer device switching to the idle mode and back. The methodaccording to the invention is characterized in what is set forth in thecharacterizing part of claim 1. The data transfer system according tothe invention is characterized in what is set forth in thecharacterizing part of claim 13. The wireless data transfer deviceaccording to the invention is characterized in what is set forth in thecharacterizing part of claim 18.

The present invention provides considerable advantages as compared tothe prior art methods and systems. With the method according to theinvention, the transfer of packets from the wireless data transferdevice can be started faster than in the prior art solutions. Inaddition, the invention can reduce the traffic on the control channelwhen a temporary block flow is formed, and thus the resources of themobile network can be used more efficiently.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

In the following, the invention will be described in more detail withreference to the accompanying drawings, in which

FIG. 1 shows a prior art protocol stack,

FIG. 2 is a schematic signalling diagram of the establishment of apacket-switched connection according to prior art,

FIG. 3 a is a schematic signalling diagram of the establishment of apacket-switched connection from the wireless data transfer device to themobile network according to a preferred embodiment of the invention,

FIG. 3 b is a schematic signalling diagram of a situation in which thereare no packets to be sent to the mobile network in the wireless datatransfer device,

FIG. 3 c is a schematic signalling diagram of the establishment of apacket-switched connection from the wireless data transfer device to themobile network according to another preferred embodiment of theinvention,

FIG. 3 d is a schematic signalling diagram of the establishment of apacket-switched connection from the wireless data transfer device to themobile network according to yet another preferred embodiment of theinvention, and

FIG. 4 shows an advantageous system in which the invention can beapplied.

DETAILED DESCRIPTION OF THE INVENTION

A wireless data transfer system of the GPRS type shown as a simplifieddiagram in FIG. 4 will be used as an example in the followingdescription of a preferred embodiment of the invention, but it is clearthat the invention is not limited to this system only, but it can alsobe applied in other message transmission systems, in whichpacket-switched data transmission is used. In a mobile network, whichuses the GPRS system, data transfer between the wireless data transferdevice MS and the support node SGSN of the mobile network is preferablyperformed via the base station BS.

The transfer of packets from the mobile network NW towards the wirelessdata transfer device MS will be discussed at first in the following. Itis assumed that the wireless data transfer device MS is in the idle modeand that it listens to the traffic of a control channel in order todetect messages possibly sent to the wireless data transfer device.

In order to start the transfer of packets, the procedure forestablishing a temporary block flow is started at first. In thefollowing example, the establishment of a temporary block flow will bedescribed using the PCCCH channel as the control channel, but thecorresponding principles can also be applied to the CCCH channel. FIG. 3a illustrates the establishment of the connection and the transfer ofpackets between the wireless data transfer device MS and the mobilenetwork NW as a schematic signalling diagram. Correspondingly, FIG. 3 billustrates a situation in which the transmission of packets from thewireless data transfer device MS is not started when the transmission ofpackets received from the mobile network NW has ended. In a situationthat there are packets of the LLC layer to be sent to the wireless datatransfer device MS from the mobile network NW, the support node SGSNstarts the establishment of a temporary connection. The wireless datatransfer device is then preferably in the idle mode and listens to thetraffic in the control channel. In order to start data transfer, apacket data traffic channel PDTCH, where resources are allocated for thepacket-switched connection, is configured (block 301). The mobilenetwork NW allocates one or more Packet Data Traffic Channels (PDTCH)for the connection. The number of channels (e.g. time slots) to beallocated depends on, for instance, the settings made by the operator ofthe mobile network NW, the Quality of Service reserved for theconnection, the packet connection properties of the receiving wirelessdata transfer device, etc. The mobile network NW sends a Packet DownlinkAssignment message to the wireless data transfer device MS. Theassignment message may contain, for instance, the Temporary FlowIdentity (TFI), timing information, on the basis of which the wirelessdata transfer device can estimate the starting time of the transmissionof data packets, and information about the time slot or periods in whichthe packets of the packet connection are transferred. In order toreceive packets, the wireless data transfer device switches to thePacket Transfer Mode and preferably starts the timer. The identifierT3190 is used for this timer in the GPRS system. After this, thewireless data transfer device starts listening to the packet datatraffic channel and receiving packets. The purpose of the timer is toprevent the wireless data transfer device from staying in the packetreception mode in error situations and when the transmission of packetshas ended. Error situations may arise when, for example, the wirelessdata transfer device cannot receive packets for some reason or themobile network does not send packets. Error situations are not dealtwith in more detail in this specification, because the procedures areknown as such.

The mobile network sends packets in the packet data traffic channelPDTCH (arrow 302). The wireless data transfer device MS receives eachpacket and sends an acknowledgement message, if the mobile network NWhas asked for it. By the acknowledgement message, the wireless datatransfer device MS can inform the mobile network NW that the packet haseither been received successfully (ACK) or that there have been errorsin the reception (NACK). If the mobile network NW has asked for thetransmission of acknowledgement messages, the wireless data transferdevice MS can also use the acknowledgement messages to notify the mobilenetwork NW of the need to transmit packets as long as the temporaryblock flow DL TBF is activated.

The mobile network NW sets information about the end of the packets inthe last packet to be transmitted (arrow 303), for example by settingthe Final Block Indicator (FBI) in the packet header field to the valuetrue (e.g. the logical mode 1). Then the wireless data transfer deviceMS knows that it was the last packet received in this block flow. Thewireless data transfer device sends an acknowledgement message to themobile network (arrow 304) and starts another timer, such as T3192 inthe GPRS system (block 305).

After the mobile network NW has received information that the lastpacket has been received, in a system according to a preferredembodiment of the invention the mobile network sends a enquiry message306 (such as Packet Power Control/Timing Advance (RRBP)), in which theenquiry information (the RRBP field in the GPRS system) has been set,and the wireless data transfer device can answer the enquiry by usingthe radio resource reserved for the wireless data transfer device MS,which was notified in the enquiry message. In addition, preferably thesame identifier TFI reserved for the wireless data transfer device aswas used in the ended block flow is used in this enquiry message.Setting the enquiry information in the message means in practice thatthe wireless data transfer device MS is expected to send a reply messagein the allocated radio resource.

If, however, the wireless data transfer device MS has packets to besent, it does not send the normal Packet Control Acknowledgementmessage, but having received this enquiry message, the wireless datatransfer device sends a PACKET_RESOURCE_REQUEST 307 to the mobilenetwork NW for establishing a temporary block flow for the transfer ofpackets, if there are packets in the wireless data transfer device MSwaiting for transmission. In addition, the wireless data transfer devicepreferably starts the timer T3168 and continues listening to the packetdata traffic channels PDTCH. In other case, the wireless data transferdevice MS replies normally with the PACKET_CONTROL_ACKNOWLEDGEMENTmessage 310 (FIG. 3 b). If the wireless data transfer device MS did senda request for the allocation of packet resources, the mobile network NWdetects that the wireless data transfer device MS has packets to be sentand can start the allocation of resources for a new temporary blockflow.

If the wireless data transfer device MS did send a resource allocationrequest 307 to the mobile network NW, it is examined whether it hassufficiently resources available at the moment for the establishment ofa block flow. If there are resources available, the mobile network NWsends a PACKET_UPLINK_ASSIGNMENT message 308 to the wireless datatransfer device MS. After the configuration measures needed forestablishing a temporary block flow have been performed, the wirelessdata transfer device MS can start the transfer of packets essentiallyimmediately (block 309). After this, operation continues in a mannerknown as such.

In a system according to another preferred embodiment of the invention,which is shown as a schematic signalling diagram in FIG. 3 c, theprocedure is the following. After the mobile network NW has receivedinformation that the last packet has been received, the mobile networksends in a data channel an assignment message 312 (such as Packet UplinkAssignment), in which the wireless data transfer device has beeninformed in which time slot it can send a temporary packet resourceallocation request 307, if required. After this, the operation continuesas shown in FIG. 3 a.

In a system according to yet another preferred embodiment of theinvention, the procedure may also be the following (FIG. 3 d). Themobile network sends 311 advantageously the last data packet again afterthe mobile network NW has received information that the last packet hasbeen received. In this retransmitted packet, the final bit has been setin the value true, and the wireless data transfer device has beenallocated a resource for sending acknowledgement. In addition, in thisrepeated packet it is also possible to try to set the value of the RRBPfield such that the wireless data transfer device MS would have as longa time as possible for sending the acknowledgement message. The wirelessdata transfer device is expected to send acknowledgement to thismessage. If the RLC layer in the wireless data transfer device has nowreceived information that there are packets to be sent to the mobilenetwork, the wireless data transfer device can send a temporary packetresource allocation request 307, as was described earlier in thisspecification, by setting a resource allocation request in theacknowledgement message.

Having received the acknowledgement message, the mobile network examineswhether the resource allocation request has been set in it. If it hasnot been set, the mobile network may repeat the transmission of thislast packet N times, where N is a value selected in advance. Then thelength of the time given to the wireless data transfer device forrequesting resources can be set as suitable in the existing systems byselecting N so that on one hand, needlessly long waiting times areavoided, and on the other hand, in practical situations the wirelessdata transfer device generally has sufficiently long a time for sendingthe resource allocation request. If the mobile network NW detected thata resource allocation request has been set, the mobile network startsthe procedure for establishing a temporary block flow and stops therepeated transmissions of the last packet. In this embodiment, thewireless data transfer device starts the timer T3192 preferably again inconnection with the transmission of the acknowledgement message.Correspondingly, the mobile network NW starts the timer T3193 again whenit has received the acknowledgement message from the wireless datatransfer device MS.

The purpose of starting the above mentioned timers T3168, T3192 is,among other things, to prevent the wireless data transfer device MS fromstaying to wait for messages sent by the mobile network NW forunnecessarily long a time in error situations, for example. Then, if thewireless data transfer device MS does not receive a packet connectionassignment message 308, for example, from the mobile network NW beforethe time set in the timer T3192 has expired, the wireless data transferdevice MS preferably switches to the idle mode in the known manner.

In a system according to yet another embodiment of the invention, themobile network NW does not automatically send a enquiry message 306after the last data packet transmitted, but the mobile network NWconcludes on the basis of the type of the information to be transferred,for example, whether a need to transfer packets from the wireless datatransfer device MS to the mobile network NW is expected. The situationlike this is for instance when the information to be transferredconsists of signalling messages of the mobile network NW and thewireless data transfer device MS, to which a reply message is expectedfrom the wireless data transfer device MS.

In a system according to yet another preferred embodiment of theinvention, the wireless data transfer device MS can conclude whether ithas a need to transmit packets to the mobile network NW after thewireless data transfer device MS has received the packets transmittedfrom the mobile network NW. Then the procedure may preferably be thefollowing. The wireless data transfer device MS sets in theacknowledgement message it sends to the last received packet theinformation that the wireless data transfer device MS may relativelysoon have a need to send packets. This information may include a mentionof a period of time after which the wireless data transfer device MSwill ask for resources for the transmission of packets, if required. Themobile network can then set time-out consideration and maintain theinformation needed to establish a new temporary block flow. In thisembodiment, the mobile network NW sends the enquiry message 306mentioned in connection with the description of the first preferredembodiment of the invention preferably after the period of time given bythe wireless data transfer device MS. As a reply to this enquirymessage, the wireless data transfer device MS sends the resourceallocation request 307 in a situation where the wireless data transferdevice MS has packets to be transmitted. However, if there are nopackets to be sent within the time specified by the time-outinformation, operation continues preferably in accordance with the priorart. By this arrangement, the use of radio resources can be reducedfurther when forming the temporary block flows.

By the arrangement according to the invention, the loading of the commoncontrol channels can be reduced, because in situations like thosedescribed above, the resource allocation request can be implemented byusing a data channel, which is assigned to at least the wireless datatransfer device in question. Resources are then released from thecontrol channels to other message transmission.

The Relative Reserved Block Period field RRBP mentioned above in thedescription of the invention can be advantageously applied in the GPRSsystem, for instance, in the following manner. There are now two bitsreserved for the field, and when the present invention is applied, theirmeaning can be defined according to the following Table 1 in a systemused as an example.

TABLE 1 The transmission block period reserved for the wireless data B0B1 transfer device 0 0 Number of TDMA frame = (N + 13) mod 2715648 0 1Number of TDMA frame = (N + 17 or N + 18) mod 2715648 1 0 Number of TDMAframe = (N + 21 or N + 22) mod 2715648 1 1 Number of TDMA frame = (N +52 or N + 78) mod 2715648

When the wireless data transfer device MS receives a message, whichcontains the transmission block period field RRBP, the wireless datatransfer device MS should send a reply message to the mobile network NWwithin ca. 60–120 ms (the first 3 alternatives of Table 3) from thereception of this message, depending on the value of the reply blockperiod field. In this preferred embodiment, one row of the transmissionblock period field (B0=1, B1=1) has been reserved for a situation inwhich a longer time is reserved for the wireless data transfer devicefor forming the reply message. In the example of Table 1, this meansthat the wireless data transfer device MS has approx. 240 ms ((N+52) mod2715648) or even approx. 360 ms ((N+78) mod 2715648) of time to form thereply message. Then the establishment of a temporary block flow from thewireless data transfer device MS to the mobile network NW can beimplemented as follows, for example.

The mobile network NW sets the final bit in the header field of the lastdata frame to the value true and the value 3 (B0=1, B1=1) to thetransmission block period, if the wireless data transfer device does nothave a temporary block flow in the direction of the mobile network atthe moment. When required, the wireless data transfer device sets in thereply message the information about the need to establish a temporaryblock flow. If, however, such a temporary block flow already exists, themobile network preferably sets the value 0 (B0=0, B1=0) in thetransmission block period field, whereby the temporary block flow fromthe mobile network in the direction of the wireless data transfer devicecan be stopped as soon as possible.

One of the advantages provided by the embodiment described above is thefact that a new enquiry message need not be sent from the mobile networkNW to the wireless data transfer device MS, and in spite of this thewireless data transfer device has more time to form the acknowledgementmessage than in the prior art solutions.

The packets to be transferred in the temporary block flows may bepackets that are used for the transfer of information of an application,in which case the information packets are transferred in the knownmanner from the application level to the lower layers of the protocolstack to be transferred as packets of the RLC/MAC layer. In theSubnetwork Dependent Convergence Protocol (SNDCP) block the packets aredivided, if required, to different queues according to the Quality ofService requirements specified for each packet. FIG. 1 shows fourQualities of Service (QoS) by way of example: first class, second class,third class and fourth class. However, with regard to the application ofthis invention it is not significant as such what kind of requirementsfor the quality of service have been set for different packets.

The SNDCP block transmits the packets via the Service Access Point (SAP)corresponding to the Quality of Service to the LLC layer. One LogicalLink Entity (LLE) for each packet queue corresponding to a Quality ofService has preferably been formed in this logical link control (LLC)layer.

The Logical Link Entity performs the operations of the LLC protocollayer, such as possible retransmissions of the packets. Below the LLClayer, in the connection point between the wireless data transfer deviceand the mobile network, there is a RLC/MAC (Radio Link Control/MediumAccess Control) layer in the protocol stack shown in FIG. 1. In aprotocol stack according to the example used here, this is implementedby one RLC block, the tasks of which include for instance requesting theallocation of resources from the mobile network for all packets sent tothe radio path.

In FIG. 1, a data transfer connection has been formed between the LLEand RLC block via the RR interface, but it is clear that an arrangementconsisting of several RLC blocks can also be used in connection with theinvention.

FIG. 4 shows the connections of a telecommunications network in apacket-switched GPRS service. In the infrastructure of the network, themain element for the GPRS services is the GPRS Support Node, GSN. It isa mobility router, which implements the connection and co-operationbetween different data networks, for example to the PSPDN (PublicSwitched Packet Data Network) via the connection Gi or to the GPRSnetwork of another operator via the connection Gp, mobility managementwith the GPRS registers via the connection Gr, and the transmission ofdata packets to wireless data transfer devices MS irrespective of theirlocation. Physically, the GPRS Support Node GSN can be integrated withthe Mobile Switching Center (MSC) or it can be a separate networkelement based on the architecture of the data network routers. User datagoes directly between the support node GSN and the base station systemBSS consisting of the base stations BTS and base station controllers BSCvia the connection Gb, but there is a signalling connection Gs betweenthe support node GSN and the mobile switching center MSC. In FIG. 4, thesolid lines between blocks represent data traffic (or the transfer ofspeech or data in digital form) and the broken lines representsignalling. Physically, data may pass transparently via the mobileswitching center MSC. The radio interface between the wireless datatransfer device MS and the fixed network goes via the base station BTSand is denoted by the reference Um. The references Abis and A denote theinterface between the base station BTS and the base station controllerBSC, and correspondingly between the base station controller BSC and themobile switching centre MSC, which is a signalling connection. Thereference Gn represents the connection between different support nodesof the same operator. The support nodes are generally divided intoGateway GPRS Support Nodes (Gateway GSN or GGSN) and Serving GPRSSupport Nodes (Serving GSN or SGSN), as shown in FIG. 4. The GSM systemis of the Time Division Multiple Access (TDMA) type, in which traffic inthe radio path takes place by time division in consecutive TDMA frames,each of which consists of several (eight) time slots. In each time slot,the information packet is sent as a radio frequency burst of finiteduration, which consists of a number of modulated bits. The time slotsare used mainly as control channels and traffic channels. The trafficchannels are used for the transfer of speech and data, and the controlchannels are used for signalling between the base station BTS and thewireless data transfer devices MS.

The RLC block according to the invention and its functionality can beimplemented in the equipment used in the present mobile communicationsystems by making changes in the parts of the programs that deal withthe implementation of the protocol stacks. In a wireless terminal MS thefunctions can be largely implemented in connection with the processingequipment CPU at least partly by programming. This processing equipmentCPU preferably comprises at least one processor, and it can be realizedby means of an Application Specific Integrated Circuit (not shown), forexample. For radio data transfer, the wireless data transfer device MSis equipped with a radio part RF, in the known manner.

The present invention is not limited to the above described embodimentsonly, but its details can be modified without departing from the scopedefined by the attached claims. The invention can also be applied in theUniversal Mobile Telecommunication System (UMTS), for example.

1. A method for transferring packets between a wireless data transferdevice and a mobile communication network, in which method fortransferring packets between a wireless data transfer device and amobile communication network there are formed temporary packet flows, inwhich data is transferred in one or more packet data traffic channelseither in a first direction from the mobile communication network to thewireless data transfer device, or in a second direction from thewireless data transfer device to the mobile communication network, andin which method, when data transfer ends in a packet flow, anotification of the end of the data transfer is added to a packet to betransmitted, wherein when the transfer of packets in said firstdirection has ended, at least one enquiry message related to a temporarypacket flow in the first direction is also sent from the mobilecommunication network to the wireless data transfer device using thetemporary packet flow in the first direction to allow the wireless datatransfer device to request establishment of a temporary packet flow inthe second direction even when the wireless data transfer device hasindicated the reception af all data blocks from the mobile communicationnetwork, and that if there are packets in the wireless data transferdevice to be sent to the mobile communication network, a responsemessage to said message is sent from the wireless data transfer device,to which in the response message the wireless data transfer device setsinformation about the need to send packets.
 2. A method according toclaim 1, characterized in that the formation of temporary block flows iscarried out by means of signalling information transmitted in one ormore control channels.
 3. A method according to claim 1, characterizedin that the processing of the information to be transmitted takes placeaccording to a protocol stack, which includes at least an RLC/MAC layer.4. A method according to claim 1, characterized in that said responsemessage is a request message for the allocation of packet resources. 5.A method according to claim 1, characterized in that advantageously thelast transmitted packet is used as the enquiry message.
 6. A methodaccording to claim 1, characterized in that the Packet PowerControl/Timing Advance message is used as the enquiry message.
 7. Amethod according to claim 1, characterized in that the Packet UplinkAssignment message is used as the enquiry message.
 8. A method accordingto claim 5, characterized in that the transmission of the enquirymessage is repeated, whereby the following steps are also performed inthe method: the wireless data transfer device transmits a reply message,to which the wireless data transfer device sets information about theneed to transmit packets, said reply message is received in the mobilecommunication network and it is examined whether said information aboutthe need to transmit packets has been set in the reply message, and ifthe information about the need to transmit packets has been set, theformation of a temporary block flow from the wireless data transferdevice to the mobile communication network is started, otherwise saidenquiry message is transmitted again.
 9. A method according to claim 1,characterized in that the mobile communication network is a GPRSpacket-switched network.
 10. A method according to claim 1, in which thewireless data transfer device has at least an active mode and an idlemode, characterized in that if the wireless data transfer device doesnot have packets to be transferred when the transfer of packets in thefirst direction is stopped, the wireless data transfer device is set tothe idle mode.
 11. A method according to claim 1, characterized in thatwhen the transfer of packets has stopped, the wireless data transferdevice sends an acknowledgement message to the mobile communicationnetwork, and that the wireless data transfer device sets in saidacknowledgement message at least information about the need to sendpackets.
 12. A method according to claim 11, characterized in that thewireless data transfer device also sets in said acknowledgement messageinformation about the time of transmission of the enquiry message.
 13. Adata transfer system, in which information is arranged to be transferredin packet form between a wireless data transfer device and a mobilecommunication network, and which data transfer system comprises: meansfor transferring packets between the wireless data transfer device andthe mobile communication network in temporary block flows, in whichinformation is arranged to be transferred in one or more packet datatraffic channels either in a first direction from the mobilecommunication network to the wireless data transfer device, or in asecond direction from the wireless data transfer device to the mobilecommunication network; and means for setting information about the endof a temporary block flow in a packet to be transmitted when datatransfer ends in the temporary block flow; wherein the data transfersystem also comprises at least: means for sending at least one enquirymessage related to the temporary packet flow in the first direction fromthe mobile communication network to the wireless data transfer devicewhen the transfer of packets in said first direction has stopped usingthe temporary packet flow in the first direction to allow the wirelessdata transfer device to request establishment of a temporary packet flowin the second direction even when the wireless data transfer device hasindicated the reception of all data blocks from the mobile communicationnetwork; means for examining whether the wireless data transfer devicecontains packets to be sent to the mobile communication network; wherebythe wireless data transfer device comprises at least: means for forminga reply message to said enquiry message; and means for settinginformation about the need to send packets in said reply message.
 14. Adata transfer system according to claim 13, characterized in that theformation of temporary block flows is arranged to be performed by meansof signalling information transmitted in one or more control channels.15. A data transfer system according to claim 13, characterized in thata protocol stack for processing the information to be transmitted hasbeen formed in the wireless data transfer device and the mobilecommunication network, and that the protocol stack comprises at least anRLC/MAC layer.
 16. A data transfer system according to claim 13,characterized in that said reply message is a request message for theallocation of packet resources.
 17. A method according to claim 13,characterized in that the mobile communication network is a GPRSpacket-switched network.
 18. A wireless data transfer device for a datatransfer system, in which information is arranged to be transferred inpacket form between the wireless data transfer device and a mobilecommunication network, and which data transfer system comprises meansfor transferring packets between the wireless data transfer device andthe mobile communication network in temporary block flows, in whichinformation is arranged to be transferred in one or more packet datatraffic channels either in a first direction from the mobilecommunication network to the wireless data transfer device, or in asecond direction from the wireless data transfer device to the mobilecommunication network, wherein the wireless data transfer device alsocomprises at least: means for receiving an enquiry message related to atemporary packet flow in the first direction sent from the mobilecommunication network, which enquiry message has been sent after thetransfer of packets has stopped in said first direction using thetemporary packet flow in the first direction to allow the wireless datatransfer device to request establishment of a temporary packet flow inthe second direction when the wireless data transfer device hasindicated the reception of all data blocks from the mobile communicationnetwork; means for examining whether the wireless data transfer devicehas packets to be sent to the mobile communication network; means forforming a reply message to said enquiry message; and means for settinginformation about the need to send packets in said reply message.
 19. Awireless data transfer device according to claim 18, characterized inthat the wireless data transfer device comprises means for sending anacknowledgement message to the mobile communication network when thetransfer of packets has stopped, and means for setting in saidacknowledgement message at least information about the need to sendpackets.
 20. A wireless data transfer device according to claim 19,characterized in that the wireless data transfer device comprises meansfor setting in said acknowledgement message information about the timeof transmission of the enquiry message.